A conventional prior art lenticular sheet comprised an array of cylindrical glass or plastic lenses or lenticules placed over an image comprising strips of image sections running parallel to the axis of the cylindrical lenticule (lenslet). While the simplest of these use only two image strips for each lens, one for the right eye and one for the left eye viewing, some present day 3D cameras use four or more image strips for each of the left and right eye images per lenticule to provide a very sophisticated device with smooth apparent relative motion of objects in the scene as the viewing angle is changed. Instances are known of 3-D pictures with as many as 18 strips per eye.
This approach to the 3D effect while suitable for pictures and especially in low ambient light conditions, is not easily adaptable to a high ambient light situation such as in avionics display technology. Anti-reflective coatings need to be applied to display surfaces for use in avionics display viewing and the rough surface of the lenticules of the prior art prevent the use of such coatings.
The present invention attempts to produce the effect of lenses by using holographic techniques to generate an optic element lenticular screen having an array of lenses in a manner similar to that of the prior art. The exact same approach cannot be used since holographic optic element lenses are very inefficient in the transmission mode at high (near normal) angles of incidence. Thus, a majority of light would pass through these lenticules undeviated and left and right eye scenes would not be distinguishable from one another. The solution to this problem is provided in more detail in the following material where in one embodiment the holographic optic element (HOE) lenticules are physically separated from one another and filtering means is provided between the image display and the array of lenticules so that the only light rays which are received from the display by the lenticules are at an angle of incidence substantially removed from normal.
It is thus an object of the present invention to provide stereoscopic viewing of an image using holographic techniques.
It is a further object of the present invention to provide an array of holographic optic elements arranged in such a manner and in combination with filtering means to provide stereoscopic viewing of images to be viewed while providing a flat lens surface.
Other objects and advantages of the present invention will be ascertained from a reading of the specification and appended claims in conjunction with the drawings wherein: